Methods and apparatus for reporting a relative state of charge of a battery

ABSTRACT

Various embodiments of the present technology may comprise methods and apparatus to determine an RSOC value of a battery. The methods and apparatus may comprise utilizing various parameters, such as voltage, current, and/or temperature to calculate the RSOC of the battery. In various embodiments, the methods and apparatus may display one of an actual RSOC and a reported RSOC. In various embodiments, the methods and apparatus may further detect changes in the relevant parameter(s), adjust the reported RSOC of the battery accordingly, and report the adjusted RSOC.

BACKGROUND OF THE TECHNOLOGY

“Battery capacity” is a measure (typically in ampere hours) of thecharge stored by the battery, and is determined by the mass of activematerial contained in the battery. The battery capacity represents themaximum amount of energy that can be extracted from the battery undercertain specified conditions. The available capacity of the battery maybe referred to as the relative state of charge (RSOC). Typicallyexpressed as a percentage, RSOC is the ratio of the remaining capacityto the full charge capacity (FCC).

Temperature affects the full charge capacity of the battery. Referringto FIG. 4, in general, as the temperature decreases, the capacitydecreases, and vice versa. Since the RSOC is computed based on thecapacity value, the RSCO also increases or decreases according totemperature. The effect of temperature on the battery capacity resultsin inaccurate reporting of the RSOC.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A more complete understanding of the present technology may be derivedby referring to the detailed description when considered in connectionwith the following illustrative figures. In the following figures, likereference numbers refer to similar elements and steps throughout thefigures.

FIG. 1 representatively illustrates a block diagram of a battery system100 in accordance with an exemplary embodiment of the presenttechnology;

FIG. 2 representatively illustrates a block diagram of a fuel gaugesystem in accordance with an exemplary embodiment of the presenttechnology;

FIG. 3 is a block diagram of a memory unit in accordance with anexemplary embodiment of the present technology;

FIG. 4 is a graph indicating a relationship between available capacityand temperature of a battery in accordance with an exemplary embodimentof the present technology;

FIG. 5 is a graph indicating a relationship between voltage, current,and remaining capacity of a battery in accordance with an exemplaryembodiment of the present technology; and

FIGS. 6A-B are a flow chart for reporting an RSOC in accordance with anexemplary embodiment of the present technology.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present technology may be described in terms of functional blockcomponents and various processing steps. Such functional blocks may berealized by any number of components configured to perform the specifiedfunctions and achieve the various results. For example, the presenttechnology may employ various temperature sensors, processing units,computations, algorithms, and the like, which may carry out a variety offunctions. In addition, the present technology may be practiced inconjunction with any number of systems, such as automotive systems,emergency charging system, and systems employed in consumer electronicsand consumer wearables, and the systems described are merely exemplaryapplications for the technology. Further, the present technology mayemploy any number of conventional techniques for measuring voltages,currents, temperatures, supplying power, consuming power, controllingpower delivery, and the like.

Methods and apparatus for reporting a relative state of charge (RSOC) ofa battery according to various aspects of the present technology mayoperate in conjunction with any suitable battery-operated apparatus. Forexample, the apparatus may comprise a cellular phone, a computer, atablet, or a camera. Referring to FIG. 1, in an exemplary embodiment ofthe present technology, methods and apparatus for reporting the relativestate of charge for a battery may operate in conjunction with a system100, such as a cellular phone or other communication system, including abattery monitoring system 105, a battery pack 110, a display unit 112, apower supply regulator circuit 116, a system LSI (Large ScaleIntegration) circuit 114, and an operation unit 113. According tovarious embodiments, the system 100 may also comprise other elements,such as a secondary battery 115 to operate a real-time clock circuit(not shown) and/or to update time of the cellular phone when thecellular phone is turned off.

The battery pack 110 provides power to the system 100, such as a powersupply for the cellular phone to be operated. The battery pack 110 maycomprise one or more batteries 130, such as a chargeable lithium ionbattery, and a temperature sensor to sense the temperature of thebattery 130. The temperature sensor may comprise any suitable device formeasuring the battery temperature. In the present embodiment, thetemperature sensor comprises a thermistor 131 that generates a voltageV_(t) which corresponds to a temperature of the battery 130. Thetemperature sensor may, however, comprise any appropriate sensor orother device or system for generating a signal corresponding to thetemperature of the battery 130.

The system 100 may comprise various other circuits, elements, andsystems to perform other functions. For example, the phone of thepresent embodiment may comprise a display unit 112, wherein the displayunit 112 may comprise a display screen, such as a liquid crystal panel,provided in the cellular phone to display characters, images, and thelike, and associated circuits to control the display.

The system 100 may further comprise an operation unit 113 for a user tocontrol the device. For example, the operation unit may comprise anysuitable interface to receive input from the user, such as a keypadincluding a dial key, a power key, and the like (not shown). To operatethe cellular phone, the operation unit 113 may output a control signalCONT. For example, if a user manipulates the power key in the operationunit 113 to start the cellular phone, an appropriate control CONT tostart the cellular phone is outputted from the operation unit 113.

In various embodiments, the system 100 may further comprise the systemlarge-scale integration (LSI) circuit 114 configured to realize variousfunctions, for example communication in the cellular phone. The LSIcircuit 114 may comprise any suitable system for the particular deviceor application, such as cell phone communication circuits, programmablelogic devices, memory devices, and the like. In the present embodiment,the LSI circuit 114 comprises a large scale integration circuit torealize various functions, for example communication in the cellularphone.

In various embodiments, the system 100 may further comprise a powersupply regulator circuit 116 to generate one or more power supplyvoltages for powering the various elements of the device. For example,the power supply regulator circuit 116 may power the LSI circuit 114 andother system elements based on the output voltage V_(b) of the battery130 and/or power from an external power source. The power supplyregulator circuit 116 may comprise a conventional power supplyregulation system for providing appropriate voltages for the variouselements.

The battery analysis circuit 105 determines the relative state of charge(i.e., remaining capacity) of the battery 130, and may do so accordingto any appropriate factors, including but not limited to the battery'sage, internal resistance, current, voltage, temperature, and/oreffective battery capacity. The battery monitoring system 105 maycomprise any suitable components for determining the battery's 130relative state of charge. For example, the battery monitoring system 105may include a microcomputer 122, a drive circuit 123, a third powersupply circuit 121, and a fuel gauge system 120.

The microcomputer 122 may control the cellular phone, for example basedon the control data CONT received from the operation unit 113. Further,the microcomputer 122 may transfer data DO outputted from the fuel gaugesystem 120 to the drive circuit 123 configured to drive the display unit112. The drive circuit 123 may drive the display unit 112 so that theremaining capacity, the temperature of the battery 30, and the like, canbe displayed on the display unit 112 based on the data DO from themicrocomputer 122. The third power supply circuit 121 may to generate apower supply voltage to operate the fuel gauge system 120, such as fromthe secondary battery 115. In various embodiments, the system 100 mayfurther comprise a timing unit (not shown) to operate various circuitsaccording to a predetermined timing cycle.

The fuel gauge system 120 responds to signals from the battery 130 andgenerates signals accordingly, for example to provide an indication ofthe remaining battery capacity on the display unit 112. The fuel gaugesystem 120 may comprise any suitable system, such as a large-scaleintegration (LSI). For example, referring to FIG. 2, the fuel gaugesystem 120 receives information from the battery pack 110 to analyzevarious functions and operational modes of the battery 130. According tovarious embodiments, the fuel gauge system 120 may communicate withother integrated circuits within the system 100, for example, the systemLSI 114 and/or the display unit 112.

The fuel gauge system 120 may comprise any appropriate components forreceiving signals from the battery and calculating and reporting therelative state of charge for the battery 130. For example, the fuelgauge system 120 of the present embodiment includes a logic unit 215 toreceive the signals and calculate the relative state of charge for thebattery 130. The fuel gauge system 120 may also include a memory 210 tostore information generated by and/or used by the logic unit 215. Thefuel gauge system 120 may further include various elements to generateand/or transfer signals, such as a selector 200, an analog-to-digitalconverter (ADC) 205, an interface (IF) circuit 220, and a current sensor225.

The fuel gauge system 120 may be configured to receive multiple signalsfrom the battery pack 110, such as the output voltage of the battery 130and/or the temperature signal from the temperature sensor. In variousembodiments, the selector 200 selectively transmits signals from thebattery pack 130. The selector 200 may comprise any suitable circuit toreceive the output voltage V_(b) and/or voltage V_(t), such as amultiplexer controlled by the logic unit 210.

The fuel gauge system 120 may further include the ADC 205, ifappropriate, to convert the output voltage V_(b) and thermistor voltageV_(t) provided via the selector 200 into a digital voltage value for useby the logic unit 215. The ADC 205 may comprise any suitableanalog-to-digital architecture, and may be selected based on aparticular application.

The fuel gauge system 120 may be configured to interact with otherelements of the system 100, such as to receive power and receive andtransmit control signals and data. In the present embodiment, the fuelgauge system 120 includes the IF circuit 220 to facilitate the exchangeof signals, such as between the logic unit 215 and the operation unit113, the power supply regulator circuit 116, and the microcomputer 122.The fuel gauge system 120 may be configured in any suitable manner,however, to facilitate interaction with the other elements of the system100.

The current sensor 225 may sense current through the battery 110. Forexample, the current sensor 225 may detect a direction of a currentI_(DD) flow, wherein the direction of the current I_(DD) flow mayindicate whether the battery 130 is in a charge state or a dischargestate. The current sensor 225 may also sense the magnitude of thecurrent flow. The current sensor 225 may comprise any suitable circuitor device for detecting the direction, and possibly magnitude, of thecurrent I_(DD) flow and provide corresponding signals to the logic unit215.

The logic unit 215 may control the fuel gauge system 120 in response toinput signals and generate corresponding output signals, such as therelative state of charge for a battery. The logic unit 215 may compriseany suitable analog or digital system, such as a hard-wired logicalcircuit configured to automatically respond to the input signals withthe appropriate output signals. In the present embodiment, the logicunit 215 comprises a circuit that may execute various operations and/orrealize various functions by executing one or more programs. The logicunit 215 may perform various calculations, perform decision-makingfunctions, and/or transmit various control functions. The logic unit 215may also receive information regarding various measured data, such astemperature data, as well as reference data stored in the memory 210.

The memory 210 stores information to be used by the fuel gauge system120, such as programs and data. The memory may comprise any appropriatetypes of memory, and may store any suitable information. For example,referring to FIG. 3, in various embodiments, the memory 210 may comprisea circuit to store programs executed by the logic unit 215 and varioustypes of data. In an exemplary embodiment, the memory 210 may compriseROM (read only memory) and RAM (random access memory). The storage areaof the memory 210 may comprise a program storage unit 300 to storevarious programs to operate the logic unit 215.

In an exemplary embodiment, the memory 210 may comprise various datastorage units to store data calculated and/or measured by the fuel gaugesystem 120. For example, the memory 210 may comprise a first datastorage unit 315 to store an actual RSOC value (RSOC_(actual)), a seconddata storage unit 320 to store a reported RSOC value (RSOC_(reported)),and a third data storage unit 325 to store temperature data.

The memory 210 may further comprise battery reference data. For example,the memory 210 may comprise an FCC data storage unit 330 that containsdata relating to the FCC value of the battery. The FCC data storage unit330 may comprise any suitable circuit or device for storing data.

The memory 210 may further comprise a voltage-temperature data storageunit 310 to store data indicating the relationship between thethermistor voltage V_(t) and the temperature. In the present embodiment,and referring again to FIG. 4, the voltage-temperature data storage unit310 may comprise a look-up table storing information corresponding tothe relationship between the temperature and the capacity.

The memory 210 may further comprise a voltage-current-RSOC data storageunit 335 to store data that describes the relationship between theoutput voltage V_(b), current I_(DD), and the RSOC, such as therelationship illustrated in FIG. 5. The data may be stored as a look-uptable. The voltage-current-RSOC data storage unit 335 may comprise opencircuit voltage (OCV) characteristics at a specified temperature, forexample 20 degrees Celsius. When graphed, the OCV characteristics may bereferred to as an OCV curve. For a particular output voltage V_(b), ifthe battery 130 is charging, the voltage-RSOC curve may increaserelative to the OCV curve, or if the battery 130 is discharging, thevoltage-RSOC curve may decrease relative to the OCV curve. The amountthat the voltage-RSOC curve increases or decreases relative to the OCVcurve depends, at least in part, on the magnitude of the current I_(DD).

The battery monitoring system 105 may monitor the battery 130 charge andreport the RSOC, for example via the display unit 112. The batterymonitoring system 105 may further adjust the RSOC reported to the userif the actual results are confusing or misleading, even if they arecorrect.

For example, the battery monitoring system 105 may monitor variousconditions, such as conditions that relate to the battery pack 110 andthe battery 130 capacity. In one embodiment, the battery monitoringsystem 105 monitors the battery 130 to determine the charging mode ofthe battery, i.e., whether the battery 130 is charging or discharging.The battery monitoring system 105 may also monitor a direction of changeof the temperature of the battery 130, i.e., whether the temperature isrising or falling. If the battery 130 is charging and the temperature ofthe battery is increasing, the RSOC may actually drop because thecapacity of the battery increases with temperature. Thus, even thoughthe battery 130 is charging, the RSOC decreases, which can be confusingto the user. Conversely, if the battery 130 is discharging and thetemperature of the battery is decreasing, the RSOC may actually increasebecause the capacity of the battery 130 decreases with temperature.Thus, even though the battery 130 is discharging, the RSOC increases,which can likewise confuse the user.

The battery monitoring system 105 may adjust the RSOC reported to theuser, for example according to the temperature and charging conditions.If (1) the battery 130 is charging and the battery 130 temperature isrising, or (2) the battery 130 is discharging and the battery 130temperature is falling, the battery monitoring system 105 may adjust thereported RSOC. For example, the battery monitoring system 105 maysuspend updating the RSOC and instead provide the most recently measuredRSOC to the user.

The battery monitoring system 105 may further monitor the battery 130conditions for appropriate conditions to resume updating the RSOC. Forexample, the battery monitoring system 105 may monitor the battery pack110 for a mode change, i.e., switching from charging to discharging orvice versa. When a mode change occurs, the battery monitoring system 105may determine the actual RSOC and compare it to the reported RSOC. Whenthe actual RSOC returns to the level of the reported RSOC, the batterymonitoring system 105 may continue reporting the actual RSOC to theuser.

The battery monitoring system 105 may adjust the reported RSOC accordingto suitable criteria and according to any appropriate process. Forexample, referring to FIG. 6, the exemplary fuel gauge system 120 of thepresent embodiment may perform various calculations and variousmeasurements to determine the RSOC. In various embodiments, the fuelgauge system 120 may display one of two RSOC values based on thetemperature and charge/discharge state of the battery 130.

In an exemplary embodiment, the current sensor 225 may determine whetherthe battery 130 is charging (i.e., the charge state) or discharging(i.e., the discharge state). For example, the current sensor 225 maycomprise a device to detect the direction of the current flow. In otherembodiments, the direction of the current I_(DD) flow may be determinedby measuring the output voltage V_(b) and utilizing the OCV curve, todetermine whether the output voltage V_(b) increased or decreasedrelative to the OCV curve. If the output voltage V_(b) decreasesrelative to the OCV curve, then the battery 130 is discharging, and ifthe output voltage increases relative to the OCV curve, then the battery130 is charging.

In an exemplary embodiment, if the battery 130 is discharging, then thefuel gauge system 120 may measure a first temperature T₁ (605). Forexample, the selector 200 may receive the thermistor voltage V_(t) fromthe thermistor 131 and the AD converter 205 may convert the thermistorvoltage V_(t) to a digital value. A digital value representing thethermistor voltage V_(t) may be transmitted to the logic unit 215 andstored in the memory 210. The temperature-voltage data storage unit 335may convert the thermistor voltage V_(t) to the first temperature T₁,measured in degrees Celsius. The first temperature T₁ may be stored inthe temperature data storage unit 325.

The fuel gauge system 120 may then obtain a second temperature T₂ (610)after a predetermined time. The fuel gauge system 120 may obtain thesecond temperature T₂ in the same manner as the first temperature T₁.

The logic unit 215 may utilize the first and second temperatures T₁, T₂stored in memory 210 to determine if the second temperature T₂ is lessthan the first temperature T₁ (i.e., T₂<T₁?) (615). If the secondtemperature T₂ is not less than the first temperature T₁, then the fuelgauge system 120 may continue to update the RSOC based on any suitablemethod for calculating the RSOC (625) and re-measure the battery flowdirection (600). The computed RSOC value may be referred to as theactual RSOC (RSOC_(actual)), and the fuel gauge system 120 may store theactual RSOC value in the memory 210, for example in the RSOC_(actual)data storage unit 315. The system 100 may display (i.e., report to theuser) the actual RSOC on the display unit 112.

If the second temperature T₂ is less than the first temperature T₁, thenthe fuel gauge system 120 may stop updating the RSOC value (620). Thesystem 100 may display (i.e., report to the user) the value of the RSOC,at the time when the logic unit 215 stops updating the RSOC, for exampleon the display unit 112 (630). The displayed RSOC value may be referredto as the reported RSOC (RSOC_(reported)), and the fuel gauge system 120may store the reported RSOC value in the memory 210, for example in theRSOC_(reported) data storage unit 320.

The fuel gauge system 120 may then recheck the direction of the currentIDD flow (635) to determine if a mode change has occurred (640). In thiscase, if a mode change has occurred, the current sense 225 may detectthat the battery 130 is now charging. If the fuel gauge system 120 doesnot detect a mode change, then the system may continue to display thereported RSOC value (RSOC_(reported)). If the fuel gauge system 120detects a mode change, then the logic unit 215 may determine whether theactual RSOC value is greater than the reported RSOC value (i.e.,RSOC_(actual)>RSOC_(reported) ?) (645).

If the actual RSOC (RSOC_(actual)) value is not greater than thereported RSOC value (RSOC_(reported)), then the display unit 112 maycontinue to display the reported RSOC value (RSOC_(reported)) (630). Ifthe actual RSOC value (RSOC_(actual)) is greater than the reported RSOCvalue, then the fuel gauge system 120 may adjust the reported RSOC(RSOC_(reported)) so that the reported RSOC (RSOC_(reported)) is equalto the actual RSOC value (i.e., RSOC_(reported) _(_)_(adj)=RSOC_(actual)) (650). In various embodiments, the reported RSOCmay be adjusted in increments according to a computed impedance valueand other suitable variables. The system 100 may display the adjustedRSOC (RSOC_(reported) _(_) _(adj)) on the display unit 112 (697). Invarious embodiments, if the reported RSOC is adjusted incrementally, thedisplayed RSOC (RSOC_(reported) _(_) _(adj)) may also changeincrementally. The fuel gauge system 120 may then recheck the directionof the current I_(DD) flow (600).

Alternatively, if the current sensor 225 initially determines that thebattery 130 is charging, then the fuel gauge system 120 may measure thethermistor voltage V_(t) and obtain a first temperature T₁ (655) and asecond temperature T₂ (660) in the same manner as described above, andstored in the memory 210, for example in the temperature data storageunit 325.

The logic unit 215 may utilize the first and second temperatures T₁, T₂stored in memory 210 to determine if the second temperature T₂ isgreater than the first temperature T₁ (i.e., T₂>T₁?) (665). If thesecond temperature T₂ is not greater than the first temperature T₁, thenthe fuel gauge system 120 may continue to update the RSOC based on anysuitable method for calculating the RSOC (670) and re-measure thedirection of the current flow (600). The RSOC value obtained may bereferred to as the actual RSOC (RSOC_(actual)) and the fuel gauge system120 may store the actual RSOC value in the memory 210, for example inthe RSOC_(actual) data storage unit 315. The system 100 may display(i.e., report to the user) the actual RSOC (RSOC_(actual)) on thedisplay unit 112.

If the second temperature T₂ is greater than the first temperature T₁,then the fuel gauge system 120 may stop updating the RSOC value (675).The system may display the value of the RSOC, at the time when the logicunit 215 stops updating the RSOC, for example on the display unit 112(680). The displayed RSOC value may be referred to as the reported RSOC(RSOC_(reported)), and the fuel gauge system 120 may store the reportedRSOC value in the memory 210, for example in the RSOC_(reported) datastorage unit 320.

The fuel gauge system 120 may then recheck the direction of the currentI_(DD) flow (685) to determine if a mode change has occurred (690). Inthis case, if a mode change has occurred, the current sensor 225 maydetect that the battery 130 is now discharging. If the fuel gauge system120 does not detect a mode change, then the system may continue todisplay the reported RSOC value. If the fuel gauge system 120 detects amode change, then the logic unit 215 may determine whether the actualRSOC value is less than the reported RSOC value (i.e.,RSOC_(actual)<RSOC_(reported) ?) (695).

If the actual RSOC value is not less than the reported RSOC value, thenthe display unit 112 may continue to display (i.e., report to the user)the reported RSOC value (680). If the actual RSOC value is less than thereported RSOC value, then the fuel gauge system 120 may adjust thereported RSOC (RSOC_(reported)) so that the reported RSOC(RSOC_(reported)) is equal to the actual RSOC value (i.e.,RSOC_(reported) _(_) _(adj)=RSOC_(actual)) (696). In variousembodiments, the reported RSOC may be adjusted in increments accordingto a computed impedance value and other suitable variables. The system100 may display (i.e., report to the user) the adjusted RSOC(RSOC_(reported) _(_) _(adj)) on the display unit 112 (698). In variousembodiments, if the reported RSOC is adjusted incrementally, thedisplayed RSOC (RSOC_(reported) _(_) _(adj)) may also changeincrementally. The fuel gauge system 120 may then recheck the directionof the current I_(DD) flow (600).

In the foregoing description, the technology has been described withreference to specific exemplary embodiments. The particularimplementations shown and described are illustrative of the technologyand its best mode and are not intended to otherwise limit the scope ofthe present technology in any way. Indeed, for the sake of brevity,conventional manufacturing, connection, preparation, and otherfunctional aspects of the method and system 100 may not be described indetail. Furthermore, the connecting lines shown in the various figuresare intended to represent exemplary functional relationships and/orsteps between the various elements. Many alternative or additionalfunctional relationships or physical connections may be present in apractical system.

The technology has been described with reference to specific exemplaryembodiments. Various modifications and changes, however, may be madewithout departing from the scope of the present technology. Thedescription and figures are to be regarded in an illustrative manner,rather than a restrictive one and all such modifications are intended tobe included within the scope of the present technology. Accordingly, thescope of the technology should be determined by the generic embodimentsdescribed and their legal equivalents rather than by merely the specificexamples described above. For example, the steps recited in any methodor process embodiment may be executed in any order, unless otherwiseexpressly specified, and are not limited to the explicit order presentedin the specific examples. Additionally, the components and/or elementsrecited in any apparatus embodiment may be assembled or otherwiseoperationally configured in a variety of permutations to producesubstantially the same result as the present technology and areaccordingly not limited to the specific configuration recited in thespecific examples.

Benefits, other advantages and solutions to problems have been describedabove with regard to particular embodiments. Any benefit, advantage,solution to problems or any element that may cause any particularbenefit, advantage or solution to occur or to become more pronounced,however, is not to be construed as a critical, required or essentialfeature or component.

The terms “comprises”, “comprising”, or any variation thereof, areintended to reference a non-exclusive inclusion, such that a process,method, article, composition or apparatus that comprises a list ofelements does not include only those elements recited, but may alsoinclude other elements not expressly listed or inherent to such process,method, article, composition or apparatus. Other combinations and/ormodifications of the above-described structures, arrangements,applications, proportions, elements, materials or components used in thepractice of the present technology, in addition to those notspecifically recited, may be varied or otherwise particularly adapted tospecific environments, manufacturing specifications, design parametersor other operating requirements without departing from the generalprinciples of the same.

The present technology has been described above with reference to anexemplary embodiment. However, changes and modifications may be made tothe exemplary embodiment without departing from the scope of the presenttechnology. These and other changes or modifications are intended to beincluded within the scope of the present technology, as expressed in thefollowing claims.

The invention claimed is:
 1. An apparatus for determining an RSOC of abattery, comprising: a current sensor responsive to a current throughthe battery; a temperature sensor responsive a temperature of thebattery; and a logic unit responsive to the current sensor and thetemperature sensor, wherein the logic unit: determines a direction ofchange of the temperature of the battery according to the temperaturesensor; determines a charging mode of the battery according to thecurrent sensor; and selects one of an actual RSOC value or apreviously-reported RSOC value according to the direction of change ofthe temperature of the battery and the charging mode of the battery. 2.The apparatus of claim 1, wherein the logic unit selects thepreviously-reported RSOC if the charging mode of the battery is chargingand the temperature of the battery is increasing.
 3. The apparatus ofclaim 1, wherein the logic unit selects the actual RSOC if the chargingmode of the battery is charging and the temperature of the battery isdecreasing.
 4. The apparatus of claim 1, wherein the logic unit selectsthe previously-reported RSOC if the charging mode of the battery isdischarging and the temperature of the battery is decreasing.
 5. Theapparatus of claim 1, wherein the logic unit selects the actual RSOC ifthe charging mode of the battery is discharging and the temperature ofthe battery increasing.
 6. A method for determining an RSOC value of abattery, comprising: determining a mode of operation of the battery,wherein the mode of operation of battery is at least one of a chargingmode and a discharging mode; measuring a first temperature; measuring asecond temperature; computing an RSOC; comparing the first to the secondtemperature to determine a temperature change; and selecting one of anactual RSOC value or a reported RSOC value based on the temperaturechange.
 7. The method of claim 6, wherein determining the mode ofoperation of the battery comprises detecting a direction of currentflow.
 8. The method of claim 6, wherein measuring the first and secondtemperature comprises utilizing a thermistor and converting a thermistorvoltage to a temperature value.
 9. The method of claim 6, wherein thereported RSOC is selected if the mode of operation of the battery is thecharging mode and the second temperature is greater than the firsttemperature.
 10. The method of claim 6, wherein the actual RSOC isselected if the mode of operation of the battery is the charging modeand the second temperature is less than or equal to the firsttemperature.
 11. The method of claim 6, wherein the reported RSOC isselected if the mode of operation of the battery is the discharging modeand the second temperature is less than the first temperature.
 12. Themethod of claim 6, wherein the actual RSOC is selected if the mode ofoperation of the battery is the discharging mode and the secondtemperature is greater than or equal to the first temperature.
 13. Themethod of claim 6, further comprising detecting a change in the mode ofoperation of the battery, wherein the change in the mode of operation,comprises one of the charging mode to the discharging mode or thedischarging mode to the charging mode.
 14. The method of claim 13,wherein if the battery mode of operation changes from the charging modeto the discharging mode, and the actual RSOC value is less than thereported RSOC value, then the reported RSOC is adjusted to equal theactual RSOC.
 15. The method of claim 13, wherein if the battery mode ofoperation changes from the discharging mode to the charging mode, andthe actual RSOC value is greater than the reported RSOC value, then thereported RSOC is adjusted to equal the actual RSOC.
 16. A system fordetermining an RSOC of a battery, comprising: a battery pack comprisingthe battery and a temperature measurement device to measure a firstvoltage representing a first temperature, and second voltagerepresenting a second temperature of the battery; a fuel gauge systemcoupled to the battery pack, comprising: a logic unit; a memory devicecoupled to the logic unit, comprising a look-up table with predetermineddata associating a voltage with a temperature; a current sensor, coupledto the logic unit, to determine a state of the battery, wherein thestate of battery is at least one of charging and discharging; whereinthe logic unit: compares the first and second temperatures; determines amode change of the state of the battery; and selects one of an actualRSOC value or a reported RSOC value; and a display unit coupled to thefuel gauge system to display the selected RSOC.
 17. The system accordingto claim 16, wherein the logic unit selects the reported RSOC if thestate of the battery is charging and the second temperature is greaterthan the first temperature.
 18. The system of claim 16, wherein thelogic unit selects the actual RSOC if the state of the battery ischarging and the second temperature is less than or equal to the firsttemperature.
 19. The system of claim 16, wherein the logic unit selectsthe reported RSOC if the state of the battery is discharging and thesecond temperature is less than the first temperature.
 20. The system ofclaim 16, wherein the logic unit selects the actual RSOC if the state ofthe battery is discharging and the second temperature is greater than orequal to the first temperature.